Couillard is a member of the Monegasque Davis Cup team since 2002, having posted a 14–10 record in singles and a 13–10 record in doubles in thirty-five ties played.

In 2013, Couillard and Benjamin Balleret played the longest professional tiebreak in known tennis history, lasting 70 points (34–36). Couillard lost the match 6–7(34), 1–6 in the third qualifying round for the USA F1 Futures in Plantation, Florida.[1]